Rubber base sheeted abrasive



April 1, 1941.

L. A. HATCH 2,236,597

RUBBER BASE SHEETED ABRASIVE Original Filed Nov. 10, 1928 iii/ 1 1 Patented Apr. 1, 1941 2,236,591 RUBBER BASE snna'rrn ABRASIVE Lloyd A. Hatch, so Paul, Minn, assignor to Minnesota Miningdv Manufacturing Company, St. Paul, Minn, a corporation of Delaware Continuation of'application Serial No. 318,390,

November 10, 1928. This application September 28, 1933, Serial No. 691,318

g ,7 Claims. (01. 51-298) This invention relates, in general, to a treatment of material, preferably in sheet form, and more particularly to, the treatment of material for the purpose of obtaining or forming composite structures of which forms of abrasives such as what is commonly known as sandpaper, is an example.

Although I hereinafter disclose the practice of my invention in connection with abrasives such as sandpaper, it will 'be understood that my invention or certain features thereof has a wider field of utility.

Composite structur s of the abrasive type, such as sandpaper or emery cloth, comprise generally (a) a base of sheet material which may be felted as in the case of paper or woven as in the case of cloth; (b) a more or less finely comminuted resistant material having abrading properties such as garnet or corundum and (c) a binder generally in the form of glue which serves to bind the abrasive to the base.

Where I have attempted to make abrasive products suitable for liquid sanding operations, including the water repellent properties of caoutchouc, and solvents therefor, planned to give the added body of the solvent to this solution, the material has been found to have an unusual- 1y high deterioration factor, particularly in storage incident to present day methods of production and distant distribution. ,Rubber in its ordinary solvents, such as benzol, when used for coating operations sufllcient to leave a residuum capable of forming a, bond for abrasive particles, has such high viscosity as to render the batch unsuitable for present methods and machlnm for applying abrasive grit or layers tothe fabric base or backing, such as cloth or paper. 'Also, where I have attempted to cover a paper base with a bond including caoutchouc, the size ordinarily used in paper reacts with the caoutchouc to embrittle and otherwise cause deterioration thereof after continued storage.

Further, where I have attempted to bind abrasive particles to a base or backing by utilizing a rubber solution in an organic solvent, the high losses in the evaporation of the organic solvent to leave the desirable rubber residuum a-re'expensive aside from the hazards involved in the readily inflammable vapors given ofi by the rubcellulose base lacquers, abrasives, whether of the glue bond type or resinous or varnish bas type or oil base type, have been found to readily load ticularly if th bond becomes somewhat softened by the heat of the abrasion process.

The objects, therefore, of my invention are the provision of an abrasive article in the nature of sandpaper including rubber as an ingredient thereof included upon a base or backing of paper or fabric in quantities holding a grit or layer of abrasive particles, the abrasive article having the property of being resistant to moistur and deterioration and having prolonged keeping qualities of predetermined flexibility; the provision of an abrasive article in the nature of sandpaper, including a bond which has great tensile strength whereby particles of the material to be abraded will not penetrate the bond and will thereby be prevented from loading the abrasive sheet, rendering inactive the abrasive particles; the provision of an abrasive article in the nature of sandpaper, .the abraslveparti-oles whereof include a bond having a tensile strength capable of resisting the penetration thereinto of the par-ti cles from an abrasive operation, yet of sufficient predetermined flexibility to have the abrasive article conform to irregular bodies in abrasive processes; the provisionfof an abrasive article in the nature of sandpaper including a rubber bonded grit or layer of I abrasive particles characterized by being resistant to moisture and liquids used in sanding operations including detergents; .the provision of an abrasive article in the nature of sandpaper including a rubber bonded grit or layer of abrasive particles, the rubber bility, the rubber being rendered stable by whollyor partially saturating with reagents, such as sulfur, sulfur chloride, hydrogen halides, oxygen, chlorine or other halogens, oxides of nitrogen or any combinations of these, the combination of some of these ingredients to produce a rubber isomer of the type a on themket under the name Thermoprene or "acid seal primer, and varying in plasticity and hardness, depending upon the degree of flexibility desired; the provision of an abrasive article in the nature of sandpaper of composite cross section, whose back pro-size, bond and sand size include rubber as a component thereof, the abrasive article being by resistance to moisture or liquids used in sanding operations including detergents and having predetermined flexibility.

Other objects of my invention reside in the provision of a binder including rubber as an ingredient thereof which may be deposited upon a I base or backing of paper or fabric in. quantities sufiicient to hold a grit or layer of abrasive partlcles, the binder having the property of bein resistant to moisture and deterioration; the provision of a binder including rubber as an ingredient thereof, which serves to saturate and adhere to the base or backing of an abrasive article characterized by having a high order to flexibility and in quantities suflioient to hold a grit or layer of abrasive particles to the base or backing.

Other objects of my invention reside in the provision of a base or backing for abrasive particles, whether in the form of woven or sheeted fabric, the fibers whereof are made resistant to disintegration or absorption of liquids such as water or liquids having a detergent action when used in liquid sanding operations, the backing being more particularly characterized by having no deteriorating effect upon an abrasive or layer including rubber as a component thereof and being still further characterized by vigorously holding a bond including rubber as an element thereof for abrasive particles; the provision of a sheeted backing or base for an abrasive article characterized by flexibility and extensibility, and resistance to aqueous liquids or aqueous liquids including detergents but one to which a binder including rubber as an element thereof may be applied and adhesively attached thereto without deterioration of the binding layer without modified interaction of the elements of the backing with the binder layer to adversely affect the property of flexibility, extensibility and resistance to the action of liquids, particularly those including detergents; the provision of a sheeted fabric in the nature of paper, treated so as to render the binder for the fibrous material thereof inactive to a coating or layer serving to bond abrasive particles, said bond including rubber as a component thereof; the provision of a sheeted fabric serving as a base or backing for an abrasive article including rubber as an element thereof, and serving to prevent disintegration of the fibrous material thereof and adhesively hold a coating for the abrasive particles so as to form an article in the nature of sandpaper.

Still further objects of my invention reside in the provision of a process for treating a base or backing for abrasive articles inthe nature of sandpaper, whether in the form of a woven web such as cloth or felted fiber, such as paper, and including rubber as a bonding agent, the process being characterized by the ability to control the abrasive article made thereof as to its flexibility, strength and resistance to deterioration; the provision of a process for introducing rubber in a sheeted fabric for abrasive articles in the nature of sandpaper; the provision of a process for treating sheeted fabric such as paper with a bond including rubber as an element thereof to control its properties of flexibility, strength and resistance to deterioration in aqueous solutions of detergents.

Still further objects of my invention reside in the provision of compositions useful for forming binders or saturating elements for the base or backing of an abrasive article in the nature of sandpaper, the composition being characterized by including rubber as an element thereof with modifying agents to control the deposition of the rubber within limits imparting flexibility, strength and ability to resist deterioration, waterproofness and binding of abrasive partcles to a sheet or backing within all ranges and sizes of grit nor,- rnally employed in articles, such as sandpaper;

Still further objects of my invention reside in the provision of a process for abrading lacquered surfaces of the character including cellulose compounds such as nitrocellulose or acetylcellulose as a. base thereof, by abrading the same, particularly in the presence of a liquid, such as water, characterized by bonding the abrasive particles with a bond having a tensile strength to resist penetration by the abraded particles characterized by using rubber as a. component of the bonding agent for the abrasive particles.

In the employment of my present invention for the production of sandpaper or the like, suitable for employment in liquid abrading operations, whether aqueous, as water, or those having a detergent action, I may use as the base sheeted material which may be paper, which will conveniently serve the employment contemplated and has as the abrasive such comminuted material which may be crushed garnet, similarly adapted to serve the function in view.

The base may be paper, such as of the absorbent character, but for my purpose it is preferred that thepaper he of the character wherein some of the size or all of it has been replaced by an aqueous emulsion of rubber, preferably vulcanized, and prepared in the manner hereinafter described. This I will generally refer to as a rubber size base or backing.

The treatment of the base according to my present invention involves primarily the association of rubber with the sheeted base, of which paper in the unsized condition is the preferred form. Rubber is introduced in a vehicle leaving a residue on the sheeted base in the nature of a surface treatment; preferably, however, as a Y vulcanizing agent. The rubber in its vehicle may be varied to leave a residuum serving as a base or backing modifier or a bond for the abrasive particles in the nature of a grit or layer to form the abrasive article. Thus, the preparation of rubber in respect to the vehicle may be varied in accordance with the purpose for which the rubber mixture is to 'be used; that is, a base modifying agent or abrasive adhesive or binder.

Thus, also, I may vary the concentration of the rubber in its vehicle for purposes of either coating or saturating, taking into account the nature'of the residuum and also the susceptibility to penetration and degree of porosity of the sheeted base.

Of the rubber that I may use, I may mention solutions of rubber in organic solvents, suspensions of rubber in aqueous vehicles or aqueous emulsions of rubber solutions in which the rubber solutions is in the internal phase. The rubber may further be of the untreated variety and after being deposited from its vehicle, may be modified by vulcanizing agents or the rubber may be incorporated in its vehicle in a condition previously modified by vulcanizing agents, or a combination of the processes wherein the vulcanizing agents are incorporated in a rubber mixture. The modifying agents may be of the character which .wholly or partially saturate the rubber by reagents such as sulfur, sulfur chloride, hydrogen halides, oxygen, chlorine or other halogens, oxides of nitrogen or any combinations of these. the combination of some of these ingredients serving to produce a rubber isomer of the type appearing on the market under the name "Thermoprene or Acid seal primer, and varying in plasticity and hardness, depending upon the degree of flexibility desired.

More specifically, the modifying agents from the combination of the ingredients .iust enumerated above, may be those which convert rubber into thermoplastic products by the action of phenol sulphonic acid, toluene sulphonyl chloride and toluene sulphonic acid.

Additionally, the modifying agents of the group of ingredients specified may be of the character which will produce an artificial isomer of rubber having less chemical unsaturation than rubber.

The association of the rubber with the base, whether paper or woven fabric may be made at the time of or subsequent to the coating of the sheet with the abrasive particles. In the case of paper, the rubber residuum may even be introduced at the time that the paper is formed. The rubber residuum may extend uniformly throughout'the base or may be applied to obtain a satisfactory base by surface treatment and limited penetration. In its simplest form, I may use a rubber treatment including unvulcanized rubber, such as fresh crepe para rubber in a vehicle, as follows:

EXAMPLE A Formula No. I

Parts by weight Rubber latex suspension (approx. 30% rubber) 400 Precipitated sulfur 8 Piperidine 1 Zinc oxide 2 In the above formula, the parts may be varied in accordance with the porosity of the base or backing and where a rubber suspension is used, carrying a varying quantity of rubber, the other ingredientswill'be accordingly modified. It will be observed that though I specify the rubber sus pension as rubber latex, this may be obtained by grinding rubber in an aqueous suspensoid or a mixture of a solution of rubber and an aqueous vehicle with the rubber solution .in the internal ,phase and the water forming the external phase. In using a solution of rubber, it is preferred to utilize solventswhich will give a solution of low viscosity, yet carrying ,a quantity of rubber to leave a large amount of rubber residuum.

In forming the abrasive article, after compounding the ingredients above enumerated in the formula, the mixture is coated by doctoring knives or rolls upon the backing or base. The sheet so treated may then be subjected to vulcanizing temperatures (approximately 130 degrees C.) to complete the reactions necessary to permit the formation of a satisfactory bond.

EXAMPLE B The rubber treatment may be practiced by first applying the rubber and then reacting the,

residuum externally with a gaseous or liquid vulcanizing agent.

Formula II A solution is formed comprising- Parts by weight Rubber latex 400 Zinc oxide 2 The rubber may be of the character previously described in Example A. This rubber mixture is coated upon the base or backing and after separation of the vehicle, either aqueous in'the case of suspensions or organic in the case of solutions, is then submitted to a cold vulcanizing treatment by coating with a vulcanizing agent in the liquid state or being subjected ,to a spray, vapor or gas EXAMPLE 0 I may utilize a solution or suspension of rubber which may be added to the backing or base in the form of an aqueous emulsion, preferably one which will leave a vulcanized rubber residuum. A mixture suitable for this purpose may be prepared as follows:

Formula II] 1000 cc. of latex (suitably preserved against coagulation as by the addition of ammonia and containing about 30% of rubber solids) had added thereto a mixture containing Precipitated sulfur grams Zine oxide. do 5 Piperidine in about 50 cc. ammoniated water ams 2%,

The mixture as above made is placed in a vulcanizer and cured about 15. to 45 minutes under a pressure of about 40 pounds per square inch. This mixture may be associated with the base or backing in a manner which will be hereinafter described to coalesce the rubber and leave the same in a film of vulcanized rubber. The flexibility of the rubber film may be altered by the quantity of sulfur included. Thus, by increas ing the sulfur component, a harder rubber may be obtained.

The rubber may be that obtained by a special modifying treatment which wfll leave a residuum from the vehicle particularly resistant to liquids used in sanding operations and one which may be effectively used in contact with the organic materials present in the size or a base or backing without deterioration.

EXAMPLE D My present form takes on the deposition of rubber, from a solution or suspension in which the rubber is a chlorinated or oxidized product in a solution or suspension, the chlorination or oxidation being carried out preliminarily to form the solution, or suspension or while the rubber is in its suspending vehicle.

. Formula IV Ground, soft rubber (substantially sulfur free) kg 350 Benzol 5000 The above mixture is placed in an interiorly enameled, jacketed kettle provided with stirring apparatus and capable of having its temperature controlled for cooling or heating. A halogen containing material is then introduced, preferably chlorine gas is passed into the mixture at the rate of 8000 to 10,000 1. per minute. The chlorination is carefully controlled by providing the device with inlet and outlet flow meters and a record kept of the hydrochloric acid and chlorine flowing out of the mixture. Chlorination is stopped as soon. as the quantity of chlorine shows a decided increase.

The product resulting is a chlorinated rubber in a benzol medium. This may be used directly or the chlorinated rubber recovered after distillation of the benzol. The benzol solution of chlorinated rubber as above derived or after resolution of the chlorinated rubber may be utilized to form an aqueous emulsion in which the chlorinated rubber forms the internal phase and the aqueous medium the external phase.

The source of the rubber may be crude or reclaimed rubber and halogenation may be procured by both chlorine and hydrochloric acid. The halogenated rubber in its vehicle, whether a solvent or as a result of forming an aqueous emulsion, may be coated upon the paper stock or formed as a part thereof during the manufacture of the paper. However, the rubber solution in the usual solvents for rubber, such as benzol, xylol, chloroform, carbon tetrachloride, etc., may be used directly for coating or saturation as the halogenated rubber solutions are available in higher concentrations of rubber and lower viscosities than untreated rubber, in its solvents. With ordinary paper stock and carrying out my invention with the halogenated rubber, I find it desirable to coat both sides of the paper with this type of rubber mixture. I may then apply a thick bond coat, particularly where I use a halogenated rubber dissolved in a volatile solvent and while in this condition, there is applied the mineral coating of abrasive particles. Exposure to a temperature of about 150 degrees F., with a good circulation of air, serves to sufliciently carry off the volatile solvent and anchor the abrasive particles to the base or backing. I may thereafter apply a thin anchoring or sizing coat over the mineral. Preferably, I use a rubber solution considerably thinner than that used for the bonding coat.

The rubber bond may be of the character which will readily become adherent to a base material of the type sized with rubber components, oil, oil and resin, natural or synthetic, or synthetic resins, and for this purpose a bond may be used which still has some of the desirable properties as recited in connection with the examples previously given herein and in which part of the rubber has been replaced with resins, natural or synthetic, rubber substitutes such as vulcanized vegetable oils, or a combination of both.

EXAMPLE E A natural resin such as rosin, or a synthetic resin, preferably of the phenol-aldehyde condensation type before final reaction to infusibility, or a rubber substitute such as factis, comprising vulcanized vegetable oils, may be used in place of the rubber in the preceding formulae mentioned in Examples A, B and D, up to forty per centum (40%). Both of the previously mentioned classes of substances may also be used in the same formula as long as the total weight of rubber replaced does not exceed the above mentioned percentage of forty per centum (40%). The synthetic resin may preferably be of the character disclosed in the application of Carlton, filed March 13, 1926, S. N. 94,597, issued into Patent No. 1,775,631, September 16, 1930. The rubber substitute may be obtained by vulcanizing oils, such as corn oil, linseed oil, China wood oil, with sulphus chloride or the like.

Formula V Up to forty per centum (40%) of rosin or intermediate synthetic resin of the character above referred to is mixed with sixty to one hundred per centum of natural rubber. (Sum total to equal 100%).

Up to forty per centum of rubber substitute, such as fact is, is mixed with sixty to one hundred per centum of natural rubber. (Sum total to equal 100%.)

Also, the two classes of substances can be used in the same formula, for example, in the following manner: Twenty parts of rosin or intermediate synthetic resin can be mixed with twenty parts of rubber substitute, and these items can be properly incorporated in sixty parts of natural rubber.

The rubber mixtures prepared as above described can be used in place of the rubber called for in the formulae previously mentioned in Ex amples A, B and D and form the solid component to which a suitable vehicle may be added.

The material may be applied to the base or backing in accordance with the examples hereinbefore described.

Generally, I may use any one of the examples for treating the'base or backing, but the form of halogenated rubber I find particularly desirable for treating a paper includes a size wherein it has been found that the sizing has no appreciable deteriorating effect upon the rubber coating.

For purposes of consideration of my invention in its preferred form, I make reference to the accompanying drawing forming a part hereof, dealing with an abrasive article in sheet form, such as sandpaper, in which Figure 1 is a section of a sheet of fabric, such as paper; 1

Figure 2 is a section similar to Figure 1, with the abrasive layer or grit bonded thereto;

Figure 3 is a section taken through a base fabric of a modification of my invention;

Figure 4 is a section taken through an abrasive article, such as sandpaper, in combination with the base shown in Figure 3, but with an abrasive layer or grit applied thereto; I

Figure 5 is a section through an abrasive, such as sandpaper, showing another modification;

Figure 6 is a section through an abrasive article showing a still further modification.

Making reference to the drawing, the compositions previously described and their method of application, they may be applied to a sheet of fabric, such as paper or cloth. As shown in Figure 1, the base fabric i is paper which has applied thereto, preferably by saturation or impregnation, rubber in a suitable vehicle to leave a rubber residuum in the fibre. The method described under Example C is particularly suitable for saturation of the paper wherein a rubber size is substituted in whole or in part for the crude resin size used by paper manufacturers. Where the impregnating solution containing the rubber leaves a relatively high quantity of residuum, this may be directly utilized to adhesively bond to the base I, the abrasive particles by the residuum 4 at the superfices. This method is particularly suitable for the production of an abrasive article where the particles of abrasive are of extremely fine; texture.

In the form shown in Figure 2, the base I and the adhesive layer or bond 4 include rubber, preferably halogenated, in which case I may include in the paper base ingredients which would change the character of normal rubber. The base I may have applied thereto a presize 2 and a back size 3, in the form shown in Figure 3. The presize and the back size may include rubber in a vehicle of any of the examples above described, but where I use the unhalogenated rubber, it is preferred to have the base I preliminarily saturated with rubber, particularly that formed by Example C, wherein an unvulcanized rubber emulsion is used as the paper size.

In Figure 4, the fabric which has the pre-size and back size layers, has then applied thereto the 4 bonding layer 4 to which is then applied the abrasive grit or layer of abrasive particles 5. The pre-size coat will serve as a better union between the bonding layer and the fibrous base I and will, also, for reasons previously. described, serve to protect the bonding layer from any deteriorating eflect due to the presence of materials used in the manufacture of paper. The back size 3 will serve to protect the fibrous material from the disintegrating effect of aqueous fluids and maintain the entire composite layer of predetermined flexibility.

In Figure 5 there is shown a still further embodiment of my invention in which a paper, rubber sized or saturated, has directly applied thereto a bonding coat 4 in which are embedded the abrasive particles 5 and then provided with a sand size coat 6. Here the base and bond coat may include rubber of the character described in Formulas 1, 2 and 3, and the sand sizing layers preferably a halogenated rubber coating. For ordinary purposes, this layer 6 may, however, be

rubber of the character described in Examples A, B or C. The halogenated sand size coat is' I preferred, due to its resistance to aqueous fluids,

lows: Anabrasive sheet, such as sandpaper made in accordance with any of the bonding agents heretofore described is utilized for the sanding of lacquered surfaces. particularly those including gelatinized cellulose as the base, such as gela-' tinized' nitrocellulose or acetylcellulose, in the presence of a liquid, such as water, preferably including a detergent to prevent dusting of the abraded particles. The abraded particles resulting from this sanding operation will not penetrate the bond of the abrasive particles nor will they load and render inactive the grit or abrasive particles of the sandpaper. The sanding may be carried out at a speed of operation which would sizing material 6, wherein there will be a compensatory action preventing undue "curling of the composite sheet so that it may lay flat in storage.

The article above made by the methods above outlined enables the production of a waterproof sandpaper and possesses resistance to materials used in liquid abrading operations, particularly those which may include detergentsand can be obtained in predetermined degrees of flexibility.

trated its use, what I claim as new and desire to secure by Letters Patent, is:

1. A new article of manufacture in the nature of flexible sandpaper comprising a flexible sheet of paper susceptible to fluid penetration, a grit or layer of abrasive-particles, and a vulcanized rubber adhesive bond interposed between said grit and said sheet, an auxiliary coat of halogenated rubber to protect said sheet and bond against water and detergents, said auxiliary coat being of the nature to maintain the bonding eflect throughout the effective abrading life of the abrasive article.

2. An adhesive for joining an abrasive article to a backing member, said adhesive containing a mixture of rubber, an isomer of rubber and a synthetic resin,

3. An abrasive article comprising a bonded abrasive article and a backing member joined to said bonded abrasive article by an adhesive containing a mixture of rubber, an isomer of rubber and a synthetic resin.

4. An abrasive article comprising a. bonded abrasive article and a backing member joined to the said bonded abrasive article by an adhesive mixture comprising soft rubber and a synthetic resin,

5. An abrasive article comprising abrasive particles and a backing member, the abrasive particles being joined to'the backing by an adhesive comprising a mixture of soft rubber and a synthetic resin.

6. An abrasive article comprising abrasive particles and a. backing member, the abrasive particles being joined to the backing by an adhesive comprising a mixture of soft .rubber and a synthetic resin of the phenolaldehyde condensation type.

7. An abrasive article comprising abrasive particles and a backing member, the abrasive particles being joined to the backing by an adhesive comprising a mixture of soft rubber and a syn thetic resin of the phenolaldehyde condensation I type at an intermediate stage and before final reaction to infusibility, in whichradhesive mixture said resin constitutes up to 40% of the total weight of the said adhesive mixture.

LLOYD A. HATCH. 

